It was the easiest choice he'd ever had to make; Castiel threw the bottle and watched his brother burn in holy fire.
It was the hardest thing he'd ever have to do; the bottle smashed into pieces, flames burst into being, and Castiel stared in horror as Adam's body burned, as his lover's flesh was scorched.
It was his last act of rebellion; for the split second it took for Lucifer to end his existence, Castiel remembered... Adam's smile, wary and unsure, but hopeful; Adam's ceaseless questioning and Castiel borrowing Dean's tried and true method of shutting Sam up, kissing those sweet lips until all Adam could think was Cas Cas Cas; sleeping, still a nerve-wracking experience, and holding the warm, breathing, the very much there form of his Adam.
Castiel had gone to hell, fought through hordes of demons to reach Dean Winchester, on orders from above.
Castiel had forsaken heaven, leaving behind the only family he'd ever known, on the faith he had in Dean's ability to end the apocalypse.
Castiel had chosen to fall, to become human, abandoning the power of heaven and the chance to go home. He'd chosen to fight with the hunters, with the humans, with Sam and Dean Winchester.
Castiel dies, praying he'd be reunited with the one precious soul he'd do absolutely anything for. Castiel gives everything he has for the love of one Adam Milligan, son of John Winchester and baby brother to Sam and Dean Winchester.
Castiel felt truly loved from the moment Adam clumsily pressed his chapped lips to Castiel's own, only weeks earlier.
It was the easiest choice he'd ever had to make and he chose Adam over everything else in his world.